Method of fabricating semiconductor device and semiconductor device

ABSTRACT

A first conductive type layer having a band gap energy smaller than that of an under growth layer formed on a substrate is formed by selective growth from an opening portion formed in the under growth layer, and an active layer and a second conductive type layer are stacked on the first conductive type layer, to form a stacked structure. When such a stacked structure for forming a semiconductor device is irradiated with laser beams having an energy value between the band gap energies of the under growth layer and the first conductive type layer, abrasion occurs at a first conductive type layer side interface between the under growth layer and the first conductive type layer, so that the stacked structure is peeled from the substrate and the under growth layer and simultaneously isolated from another stacked structure for forming another semiconductor device. Since the first conductive layer has good crystallinity and is suitable for formation of an electrode thereon, an electrode can be efficiently formed on the back surface of the first conductive type layer of the peeled stacked structure.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a method of fabricating asemiconductor device and a semiconductor device fabricated by thefabrication method, and particularly to a method of fabricating asemiconductor device using nitride based compound semiconductors, whichis capable of peeling an under growth layer together with a growthsubstrate and efficiently forming an electrode on the back surface of afirst conductive type layer, and a semiconductor device fabricated bythe fabrication method.

[0002] A technique of peeling semiconductor growth layers stacked on asapphire substrate from the sapphire substrate by etching has beenknown. The peeling technique using etching, however, has a problemassociated with a slow etching rate and damage of a crystal plane byetching.

[0003] In particular, since it is difficult to peel nitride basedcompound semiconductor growth layers from a sapphire substrate by wetetching, the nitride based compound semiconductor growth layers havebeen peeled from the sapphire substrate by dry etching such as reactiveion etching. In this case, however, since a corrosive gas is used forreactive ion etching, a crystal plane is generally damaged by thecorrosive gas.

[0004] To cope with such problems caused in peeling semiconductor growthlayers from a growth substrate by etching, there has been developed amethod of peeling semiconductor growth layers from a growth substrate byirradiating the semiconductor growth layers with laser beams travelingfrom the back side of the growth substrate, to cause abrasion at theinterface between the semiconductor growth layers and the growthsubstrate, thereby peeling the semiconductor growth layers from thegrowth substrate.

[0005] In the case of nitride based compound semiconductor growthlayers, when the semiconductor growth layers stacked on a sapphiresubstrate are irradiated with laser beams traveling from the back sideof the sapphire substrate, an undoped layer and a buffer layer of thesemiconductor growth layers absorb the laser beams, to cause abrasion,whereby the semiconductor growth layers are peeled, together with theundoped layer and the buffer layer, from the sapphire substrate. Theundoped layer and buffer layer are then etched and an electrode isformed on the back surface of a semiconductor device portion of thepeeled semiconductor growth layers.

[0006] Such a peeling method using laser abrasion, however, has problemsthat since the undoped layer and the buffer layer on the back surface ofthe semiconductor growth layers peeled from the sapphire substrate havea polycrystalline or amorphous structure having a high resistance, it isnot appropriate to form an electrode on the undoped layer and the bufferlayer, and since the undoped layer and the buffer layer are etched, thefabrication efficiency is degraded.

[0007] In the case of forming an electrode on the back surface of asemiconductor device portion of semiconductor growth layers, if the backsurface of the semiconductor growth layers is etched, the number ofsteps of fabricating a semiconductor device is increased, to increasethe fabrication cost of the semiconductor device, thereby increasing thefabrication cost of an image display unit using the semiconductordevices.

[0008] For nitride based compound semiconductor growth layers, to forman electrode on the back surface of a device portion of thesemiconductor growth layers, the back surface of the device portioncannot be etched by wet etching. Therefore, it is etched by dry etchingsuch as reactive ion etching, with a result that an undoped layer and abuffer layer on which the electrode is to be formed are significantlydamaged by a corrosive gas used for dry etching.

SUMMARY OF THE INVENTION

[0009] An object of the present invention is to provide a method offabricating a semiconductor device, which is capable of peeling an undergrowth layer together with a growth substrate, and efficiently formingan electrode on the back surface of a first conductive type layer, andto provide a semiconductor device fabricated by the fabrication method.

[0010] To achieve the above object, according to a first embodiment ofthe present invention, there is provided a method of fabricating asemiconductor device, including the steps of: forming an under growthlayer on a substrate; forming an anti-growth film having a specificopening portion on the under growth layer; forming a first conductivetype layer by selective growth from the opening portion, the firstconductive type layer having band gap energy smaller than that of theunder growth layer; stacking an active layer and a second conductivetype layer on the first conductive type layer, to form a stackedstructure; and peeling the stacked structure from the substrate and theunder growth layer at an interface between the under growth layer andthe first conductive type layer by irradiating the stacked structurewith light rays traveling through the substrate.

[0011] According to a second embodiment of the present invention, thereis provided a semiconductor device including: an under growth layerformed on a substrate; an anti-growth film, having a specific openingportion, formed on the under growth layer; a first conductive type layerformed by selective growth from the opening portion, the firstconductive type layer having band gap energy smaller than that of theunder growth layer; and an active layer and a second conductive typelayer stacked on the first conductive type layer, to form a stackedstructure; wherein the stacked structure is peeled from the substrateand the under growth layer at an interface between the under growthlayer and the first conductive type layer by irradiating the stackedstructure with light rays traveling through the substrate.

[0012] The method of fabricating a semiconductor device and thesemiconductor device fabricated by the fabrication method according tothe present invention have the following advantages:

[0013] In general, semiconductor growth layers formed on a growthsubstrate are peeled from the growth substrate due to abrasion caused byirradiating the semiconductor growth layers with laser beams travelingfrom the back side of the growth substrate. With this laser abrasion,according to the above-described configuration of the first embodimentof the present invention, since the first conductive type layer of thestacked structure has band gap energy smaller than that of the undergrowth layer and laser beams emitted to the back side of the growthsubstrate for irradiation of the stacked structure have an energy valuebetween the band gap energies of the under growth layer and the firstconductive type layer, abrasion occurs at a first conductive type layerside interface between the under growth layer and the first conductivetype layer. Accordingly, the stacked structure can be peeled at theinterface between the under growth layer and the first conductive typelayer. In other words, the under growth layer and a buffer layer can besimply peeled, together with the growth substrate from the stackedstructure. An electrode can be efficiently formed on the back surface ofthe first conductive type layer of the stacked structure thus simplypeeled. As a result, it is possible to reduce the fabrication cost of asemiconductor device.

[0014] At the time of peeling the stacked structure of the semiconductorgrowth layers from the growth substrate, the under growth layer and thebuffer layer can be peeled from the stacked structure, the surface ofthe first conductive layer, on which an electrode is to be formed, canbe treated not by dry etching such as reactive ion etching liable tocause large damage of crystal but by wet etching performed, for example,using acid with less damage of crystal. As a result, an electrode can beformed on the first conductive type layer, which has good crystallinity,with less damage of crystal.

[0015] According to the present invention, in the case of peeling thestacked structure composed of the first conductive type layer, theactive layer, and the second conductive type layer from the substratedue to abrasion caused by irradiating the stacked structure with laserbeams traveling from the back side of the substrate, the stackedstructure can be simultaneously peeled from the under growth layer andthe buffer layer having a high resistance polycrystalline or amorphousstructure, so that an electrode can be efficiently formed on the backsurface of the first conductive type layer that has good crystallinityand thereby suitable for forming an electrode thereon. Since theelectrode can be efficiently formed, the fabrication cost of asemiconductor device can be reduced, with a result that the fabricationcost of an image display unit on which the semiconductor devices aremounted can be reduced.

[0016] Each of the stacked structures composed of the first conductivelayer, the active layer, and the second conductive layer formed byselective growth is bonded to the growth substrate via the under growthlayer; however, the stacked structures are separated from each other. Asa result, when peeled from the growth substrate and the under growthlayer, the stacked structures can be simultaneously isolated from eachother. A number of the stacked structures, each containing a number ofsemiconductor devices, can be thus efficiently peeled from the growthsubstrate and the under growth layer and simultaneously isolated fromeach other.

[0017] In the case of peeling the stacked structure composed of thefirst conductive type layer, the active layer, and the second conductivetype layer due to abrasion caused by laser irradiation, it is possibleto peel a desired device portion of the stacked structure from thegrowth substrate and the under growth layer by selectively irradiatingthe desired device portion with laser beams or forming a mask forselectively collecting or shielding the laser beams.

[0018] The growth substrate and the under growth layer, from which thestacked structure has been peeled, can be reused by etching the surfacesthereof with acid. In the case of fabricating a semiconductor deviceusing nitride based compound semiconductors having a large latticemismatching with a growth substrate, it takes a large cost to fabricatethe growth substrate provided with the under growth layer on whichsemiconductor growth layers are to be formed. In this regard, by reusingthe growth substrate and the under growth layer, it is possible toreduce the fabrication cost.

[0019] Unlike a related art semiconductor device in which only a growthsubstrate is peeled or a middle portion of a under growth layer ispeeled, according to the semiconductor device of the present invention,since the under growth layer is peeled together with the growthsubstrate, it is possible to reduce the size of the semiconductor deviceas compared with the related art semiconductor device. In the case ofmounting the devices of the present invention, if each of the devices iscovered with a resin for easy handling, since the electrode is formed onthe back surface of the device, it is possible to carry out variousforms of wiring to the device.

[0020] Additional features and advantages of the present invention aredescribed in, and will be apparent from, the following DetailedDescription of the Invention and the Figures.

BRIEF DESCRIPTION OF THE FIGURES

[0021]FIGS. 1A and 1B are a sectional view and a perspective view,respectively, showing the step of forming an under growth layer in amethod of fabricating a semiconductor device according to a firstembodiment of the present invention.

[0022]FIGS. 2A and 2B are a sectional view and a perspective view,respectively, showing the step of forming an anti-growth film in themethod of fabricating a semiconductor device according to the firstembodiment of the present invention.

[0023]FIGS. 3A and 3B are a sectional view and a perspective view,respectively, showing the step of forming an opening portion in themethod of fabricating a semiconductor device according to the firstembodiment of the present invention.

[0024]FIGS. 4A and 4B are a sectional view and a perspective view,respectively, showing the step of forming a first conductive type layerin the method of fabricating a semiconductor device according to thefirst embodiment of the present invention.

[0025]FIGS. 5A and 5B are a sectional view and a perspective view,respectively, showing the step of forming an active layer and a secondconductive type layer in the method of fabricating a semiconductordevice according to the first embodiment of the present invention.

[0026]FIGS. 6A and 6B are a sectional view and a perspective view,respectively, showing the step of forming a p-side electrode in themethod of fabricating a semiconductor device according to the firstembodiment of the present invention.

[0027]FIGS. 7A and 7B are a sectional view and a perspective view,respectively, showing the step of peeling the growth substrate and theunder growth layer in the method of fabricating a semiconductor deviceaccording to the first embodiment of the present invention.

[0028]FIGS. 8A and 8B are a sectional view and a perspective view,respectively, showing the step of forming an n-side electrode in themethod of fabricating a semiconductor device according to the firstembodiment of the present invention.

[0029]FIGS. 9A and 9B are a sectional view and a perspective view,respectively, showing the step of forming an under growth layer and ananti-growth layer in a method of fabricating a semiconductor deviceaccording to a second embodiment of the present invention.

[0030]FIGS. 10A and 10B are a sectional view and a perspective view,respectively, showing the step of forming an opening portion in themethod of fabricating a semiconductor device according to the secondembodiment of the present invention.

[0031]FIGS. 11A and 11B are a sectional view and a perspective view,respectively, showing the step of forming a first conductive type layerin the method of fabricating a semiconductor device according to thesecond embodiment of the present invention.

[0032]FIGS. 12A and 12B are a sectional view and a perspective view,respectively, showing the step of forming an active layer and a secondconductive type layer in the method of fabricating a semiconductordevice according to the second embodiment of the present invention.

[0033]FIGS. 13A and 13B are a sectional view and a perspective view,respectively, showing the step of forming a p-side electrode in themethod of fabricating a semiconductor device according to the secondembodiment of the present invention.

[0034]FIGS. 14A and 14B are a sectional view and a perspective view,respectively, showing the step of peeling the growth substrate and theunder growth layer in the method of fabricating a semiconductor deviceaccording to the second embodiment of the present invention.

[0035]FIGS. 15A and 15B are a sectional view and a perspective view,respectively, showing the step of forming an n-side electrode in themethod of fabricating a semiconductor device according to the secondembodiment of the present invention.

[0036]FIGS. 16A and 16B are a perspective view and a bottom view,respectively, showing the step of peeling part of a stacked structure,which is composed of the first conductive layer, the active layer, andthe second conductive type layer formed by the fabrication methodaccording to the second embodiment, from the growth substrate and theunder growth layer.

DETAILED DESCRIPTION OF THE INVENTION

[0037] First Embodiment

[0038] A first embodiment will be described with reference to FIGS. 1Ato 8B. In this embodiment, the present invention is applied to a methodof fabricating a semiconductor light emitting device of a hexagonalpyramid shape having an approximately triangular cross-section byselective crystal growth.

[0039]FIGS. 1A and 1B are a sectional view and a perspective view,respectively, showing a step of forming an under growth layer in thefabrication method according to the first embodiment.

[0040] An under growth layer 12 is formed on a growth substrate 11. Anysubstrate may be used as the growth substrate 11 insofar as a wurtzitetype compound semiconductor layer is formable thereon. For example, asapphire substrate with a C-plane of sapphire taken as a principal planeof the substrate, which has been often adopted for growth of galliumnitride (GaN) based compound semiconductors, may be used as the growthsubstrate 11. It is to be noted that the C-plane of sapphire taken as aprincipal plane of the substrate is not limited to a strict C-plane butmay be tilted therefrom in a range of 5° to 6°. In particular, accordingto the first embodiment, since stacked structures formed on the growthsubstrate 11 via the under growth layer 12 are to be irradiated withlaser beams traveling from the back side of the growth substrate 11 atthe time of peeling the growth substrate 11 and the under growth layer12 from the stacked structures in the subsequent step, the growthsubstrate 11 is preferably configured as a light permeable substratesuch as a sapphire substrate.

[0041] The under growth layer 12 formed on the principal plane of thegrowth substrate 11 may be made from a wurtzite type compoundsemiconductor. This is because a wurtzite type compound semiconductorlayer having a hexagonal pyramid structure is to be formed on the undergrowth layer 12 in the subsequent step. For example, the under growthlayer 12 may be made from a group III based compound semiconductor;specifically, a gallium nitride (GaN) based compound semiconductor,aluminum nitride (AlN) based compound semiconductor, indium nitride(InN) based compound semiconductor, indium gallium nitride (InGaN) basedcompound semiconductor, or aluminum gallium nitride (AlGaN) basedcompound semiconductor.

[0042] The under growth layer 12 may be grown by any known vapor phasegrowth process; for example, metal organic chemical vapor deposition(MOCVD) (which is also called a metal organic vapor phase epitaxialgrowth (MOVPE) process), a molecular beam epitaxial growth (MBE)process, or a hydride vapor phase epitaxial growth (HVPE) process. Inparticular, the MOVPE process is advantageous in growing the undergrowth layer with good crystallinity at a high processing rate. Whilenot shown in FIGS. 1A and 1B, a specific buffer layer may be formed onthe bottom side of the under growth layer 12.

[0043] An impurity such as silicon is generally doped in the entireunder growth layer 12 because the under growth layer 12 functions as aconductive layer on which an n-side electrode is to be formed. Accordingto the first embodiment, however, it is not required to dope anyimpurity in the under growth layer 12. The reason for this is that, aswill be described later, at the time of peeling the growth substrate 11from stacked structures by abrasion caused by irradiating the stackedstructures with laser beams traveling from the back side of the growthsubstrate 11, the under growth layer 12 is to be peeled together withthe growth substrate 11. That is to say, it is not required to dope anyimpurity in the under growth layer 12 to be peeled together with thegrowth substrate 11.

[0044]FIGS. 2A and 2B are a sectional view and a perspective view,respectively, showing the step of forming an anti-growth film in thefabrication method according to the first embodiment.

[0045] An anti-growth film 13 made from silicon oxide or silicon nitrideis formed as a mask layer on the overall surface of the under growthlayer 12 by a sputtering process or the like.

[0046]FIGS. 3A and 3B are a sectional view and a perspective view,respectively, showing the step of forming opening portions in thefabrication method according to the first embodiment.

[0047] Opening portions 13 a are formed in the anti-growth film 13functioning as the mask layer. In general, the shape of each openingportion 13 a used for selective growth is not particularly limitedinsofar as a facet structure having a tilt plane tilted from theprincipal plane of the growth substrate 11 can be formed by selectivegrowth from the opening portion 13 a. For example, the opening portion13 a may be formed into a stripe shape, a rectangular shape, a circularshape, an elliptic shape, a triangular shape, or a polygonal shape suchas a hexagonal shape. The surface of the under growth layer 12, locatedunder the anti-growth film 13, is exposed from the opening portions 13a. According to the first embodiment, since a stacked structure composedof a first conductive layer, an active layer, and a second conductivetype layer is to be formed into a hexagonal pyramid shape having anapproximately triangular cross-section by selective growth from theopening portion 13 a, the opening portion 13 a may be formed into acircular shape or a hexagonal shape. The opening portion 13 a shown inFIGS. 3A and 3B is formed into a circular shape.

[0048]FIGS. 4A and 4B are a sectional view and a perspective view,respectively, showing the step of forming a first conductive type layerin the fabrication method according to the first embodiment.

[0049] A first conductive type layer 14 is formed by selective growthfrom each of the opening portions 13 a having the circular shape. Likethe under growth layer 12, the first conductive type layer 14 is madefrom a wurtzite type compound semiconductor such as GaN doped withsilicon. The first conductive type layer 14 functions as an n-typecladding layer. If a sapphire substrate with the C-plane of sapphiretaken as a principal plane of the substrate is used as the growthsubstrate 11, the first conductive type layer 14 is formed into ahexagonal pyramid shape having an approximately triangular cross-sectionby selective growth as shown in FIG. 4B.

[0050] According to the first embodiment, band gap energy of asemiconductor material forming the first conductive type layer 14 isrequired to be smaller than that of a semiconductor material forming theunder growth layer 12. To meet such a requirement, for example, theunder growth layer 12 may be made from AlGaN and the first conductivelayer 14 may be made from GaN.

[0051]FIGS. 5A and 5B are a sectional view and a perspective view,respectively, showing the step of forming an active layer and a secondconductive type layer in the fabrication method according to the firstembodiment.

[0052] An active layer 15 and a second conductive type layer 16 arestacked in this order on the first conductive type layer 14.

[0053] The active layer 15 functions as a light emission layer of asemiconductor light emitting device, and is configured as an InGaN layeror as an InGaN sandwiched between AlGaN layers. The active layer 15extends along the facet composed of the tilt planes of the firstconductive type layer 14. The thickness of the active layer 15 is set toa value that is suitable for light emission. The active layer 15 may beconfigured as a single bulk active layer but may be configured as alayer having a quantum well structure such as a single quantum well(SQW) structure, a double quantum well (DQW) structure, or a multiplequantum well (MQW) structure. If the active layer 15 is configured as alayer having the multiple quantum well structure, a barrier layer may beused for separating quantum wells from each other as needed.

[0054] The second conductive type layer 16 is made from a wurtzite typecompound semiconductor such as GaN doped with magnesium. The secondconductive type layer 16 functions as a p-type cladding layer. Thesecond conductive type layer 16 also extends along the facet composed ofthe tilt planes of the first conductive type layer 14. The tilt plane ofthe hexagonal pyramid shape formed by selective growth may be selectedfrom an S-plane, a (11-22) plane, and planes substantially equivalentthereto.

[0055]FIGS. 6A and 6B are a sectional view and a perspective view,respectively, showing the step of forming a p-side electrode in thefabrication method according to the first embodiment.

[0056] A p-side electrode 17 is formed on the surface of the secondconductive type layer 16, which is the outermost layer of the hexagonalpyramid shaped stacked structure composed of the first conductive typelayer 14, the active layer 15, and the second conductive type layer 16.For example, the p-side electrode 17 has a stacked metal structure ofNi/Pt/Au or Pd/Pt/Au formed by a vapor-deposition process. It is to benoted that an n-side electrode is formed on the back surface of thehexagonal pyramid shaped stacked structure and, therefore, it is notformed in this step.

[0057]FIGS. 7A and 7B are a sectional view and a perspective view,showing the step of peeling the growth substrate 11 and the under growthlayer 12 from the hexagonal pyramid shaped stacked structures byirradiating the hexagonal pyramid shaped stacked structures with laserbeams traveling from the back side of the growth substrate in thefabrication method according to the first embodiment, respectively.

[0058] Laser beams such as excimer laser beams as ultraviolet laserbeams or YAG laser beams may be emitted to the overall back surface ofthe growth substrate or regions, corresponding to target semiconductorlight emitting devices, of the back surface of the growth substrate 11.

[0059] Since the band gap energy of the first conductive layer 14 is, asdescribed above, smaller than that of the under growth layer 12, iflaser beams having an energy value between these band gap energies isused as the laser beams emitted to the back side of the growth substrate11, the laser beams are not absorbed by the under growth layer 12 butare absorbed by the first conductive type layer 14. Accordingly, since afirst conductive type layer 14 side interface between the under growthlayer 12 and the first conductive type layer 14 absorbs the laser beams,abrasion occurs at the first conductive type layer 14 side interface,with a result that the growth substrate 11 is peeled, together with theunder growth layer 12, from the hexagonal pyramid shaped stackedstructures.

[0060] In the case where the under growth layer 12 is made from AlGan(Al content: about 15%) and the first conductive type layer 14 (dopedwith silicon) is made from GaN having band gap energy smaller than thatof AlGaN, if third harmonic YAG laser beams (355 nm) are emitted to theback side of the growth substrate 11, the first conductive type layer 14side interface between the under growth layer 12 and the firstconductive type layer 14 absorbs the YAG laser beams, so that GaN isdecomposed into gallium (Ga) and nitrogen at the first conductive typelayer 14 side interface, with the result that the growth substrate 11and the under growth layer 12 are easily peeled from the hexagonalpyramid shaped stacked structures.

[0061] The band gap energy of AlGaN (Al content: about 15%) forming theunder growth layer 12 is 3.8 eV, the band gap energy of GaN forming thefirst conductive type layer 14 is 3.2 eV, and the energy of the thirdharmonic YAG laser beams (355 nm) is 3.5 eV. Accordingly, the YAG laserbeams are not absorbed by the under growth layer 12 but absorbed by thefirst conductive type layer 14, with a result that abrasion occurs atthe first conductive layer 14 side interface.

[0062] As described above, when the hexagonal pyramid shaped stackedstructure including the first conductive layer 14 made from asemiconductor material having band gap energy smaller than that of theunder growth layer 12 is irradiated with laser beams having an energyvalue between the band gap energies of the two layers 12 and 14, thelaser beams are not absorbed by the under growth layer 12 but absorbedby the first conductive type layer 14. Accordingly, the first conductivetype layer 14 side interface between the under growth layer 12 and thefirst conductive type layer 14 absorbs the laser beams, and therebyabrasion occurs at the first conductive type layer 14 side interface,with a result that the growth substrate 11 and the under growth layer 12are easily peeled from the hexagonal pyramid shaped stacked structure.

[0063] Each of the hexagonal pyramid shaped stacked structures, which iscomposed of the first conductive layer 14, the active layer 15, and thesecond conductive layer 16 formed by selective growth, is bonded to thegrowth substrate 11 via the under growth layer 12. However, thesehexagonal pyramid shaped stacked structures are separated from eachother. Accordingly, when peeled from the growth substrate 11 and theunder growth layer 12, the hexagonal pyramid shaped stacked structuresare simultaneously isolated from each other.

[0064] As a result, a number of hexagonal pyramid shaped stackedstructures corresponding to individual semiconductor light emittingdevices can be efficiently peeled from the growth substrate 11 and theunder growth layer 12 and simultaneously isolated from each other.

[0065]FIGS. 8A and 8B are a sectional view and a perspective view,respectively, showing the step of an n-side electrode in the fabricationmethod according to the first embodiment.

[0066] The back surface of each hexagonal pyramid shaped stackedstructure (corresponding to a semiconductor light emitting device) isetched with acid or the like, and an n-side electrode 18 typicallyhaving a Ti/Al/Pt/Au electrode structure is formed thereon by thevapor-deposition process or the like.

[0067] The method according to the first embodiment described above hasthe following advantages.

[0068] Since the band gap energy of the first conductive type layer 14is smaller than that of the under growth layer 12, when the laser beamshaving an energy between the band gap energies of the layers 12 and 14are emitted to the back side of the growth substrate 11, the laser beamsare not absorbed by the under growth layer 12 but absorbed by the firstconductive layer 14. Accordingly, the first conductive type layer 14side interface between the under growth layer 12 and the firstconductive type layer 14 absorbs the laser beams, and thereby abrasionoccurs at the first conductive type layer 14 side interface. As aresult, the growth substrate 11 can be simply peeled, together with theunder growth layer 12, from the hexagonal pyramid shaped stackedstructure, and the n-side electrode 18 can be efficiently formed on theexposed back surface of the first conductive type layer 14 of the peeledhexagonal pyramid shaped stacked structure.

[0069] Each of the hexagonal pyramid shaped stacked structures, which iscomposed of the first conductive layer 14, the active layer 15, and thesecond conductive layer 16 formed by selective growth, is bonded to thegrowth substrate 11 via the under growth layer 12. However, thesehexagonal pyramid shaped stacked structures are separated from eachother. Accordingly, when peeled from the growth substrate 11 and theunder growth layer 12, the hexagonal pyramid shaped stacked structuresare simultaneously isolated from each other.

[0070] As a result, according to the first embodiment, a number ofhexagonal pyramid shaped stacked structures corresponding to individualsemiconductor light emitting devices can be efficiently peeled from thegrowth substrate 11 and the under growth layer 12 and simultaneouslyisolated from each other.

[0071] Second Embodiment

[0072] A second embodiment will be described with reference to FIGS. 9Ato 15B. In this embodiment, the present invention is applied to a methodof fabricating a semiconductor light emitting device of a triangularprism shape having an approximately triangular cross-section byselective crystal growth.

[0073]FIGS. 9A and 9B are a sectional view and a perspective view,respectively, showing a step of forming an under growth layer and ananti-growth film in the fabrication method according to the secondembodiment.

[0074] Like the first embodiment, an under growth layer 32 is formed ona growth substrate 31, and an anti-growth film 33 is formed on the undergrowth layer 32. While not shown in FIGS. 9A and 9B, a specific bufferlayer may be formed on the bottom side of the under growth layer 32.

[0075] Any substrate may be used as the growth substrate 31 insofar as awurtzite type compound semiconductor layer is formable thereon. Like thefirst embodiment, since stacked structures formed on the growthsubstrate 31 via the under growth layer 32 are to be irradiated withlaser beams traveling from the back side of the growth substrate 31 atthe time of peeling the growth substrate 31 and the under growth layer32 from the stacked structures in the subsequent step, the growthsubstrate 31 is preferably configured as a light permeable substratesuch as a sapphire substrate.

[0076] The under growth layer 32 may be made from a wurtzite typecompound semiconductor such as a gallium nitride (GaN). This is becausea wurtzite type compound semiconductor layer having a hexagonal pyramidstructure is to be formed on the under growth layer 32 in the subsequentstep. The under growth layer 32 may be grown by the metal organicchemical vapor deposition (MOCVD) (which is also called the metalorganic vapor phase epitaxial growth (MOVPE) process). An impurity suchas silicon is generally doped in the under growth layer 32 because theunder growth layer 32 functions as a conductive layer on which an n-sideelectrode is to be formed. According to the second embodiment, however,it is not required to dope any impurity in the under growth layer 32.The reason for this is that as will be described later, at the time ofpeeling the growth substrate 31 from stacked structures by abrasioncaused by irradiating the stacked structures with laser beams travelingfrom the back side of the growth substrate 31, the under growth layer 32is to be peeled together with the growth substrate 31.

[0077] The anti-growth film 33 made from silicon oxide or siliconnitride is formed as a mask layer by the sputtering process or the like.

[0078]FIGS. 10A and 10B are a sectional view and a perspective view,respectively, showing the step of forming stripe shaped opening portionsin the fabrication method according to the second embodiment.

[0079] Opening portions 33 a are formed in the anti-growth film 33. Ingeneral, each of the opening portions 33 a is formed into a stripeshape, a circular shape, or the like, allowing a facet structure havinga tilt plane tilted from the principal plane of the growth substrate 31to be formed by selective growth from the opening portion 33 a.

[0080] In particular, according to the second embodiment, to form atriangular prism shaped stacked structure having an approximatelytriangular cross-section composed of a first conductive type layer, anactive layer, and a second conductive type layer by selective growthfrom the opening portion 33 a, the opening portion 33 a is formed into astripe shape.

[0081] The shape of the opening portion 33 a, however, is not limited toa stripe shape but may be any other shape insofar as the shape of theopening portion 13 a allows a triangular prism shaped stacked structurehaving an approximately triangular cross-section composed of a firstconductive type layer, an active layer, and a second conductive typelayer to be formed by selective growth from the opening portion 33 a.

[0082]FIGS. 11A and 11B are a sectional view and a perspective view,respectively, showing the step of forming a first conductive type layerin the fabrication method according to the second embodiment.

[0083] A first conductive layer 34 is formed into a shape depending onthe shape of the opening portion 33 a by selective growth from theopening portion 33 a. According to the second embodiment, since theopening portion 33 a has a stripe shape, the first conductive type layer34 of a triangular prism shaped stacked structure having anapproximately triangular cross-section, which has a facet structurehaving tilted planes from the growth substrate 31, is formed byselective growth from the opening portion 33 a.

[0084] The first conductive type layer 34 is made from a wurtzite typecompound semiconductor such as GaN doped with silicon. The firstconductive type layer 34 functions as an n-type cladding layer.According to the second embodiment, band gap energy of a semiconductormaterial forming the first conductive type layer 34 is required to besmaller than that of a semiconductor material forming the under growthlayer 32. To meet such a requirement, for example, the under growthlayer 32 may be made from AlGaN and the first conductive layer 34 may bemade from GaN.

[0085]FIGS. 12A and 12B are a sectional view and a perspective view,respectively, showing an active layer and a second conductive type layerin the fabrication method according to the second embodiment.

[0086] Like the first embodiment, an active layer 35 and a secondconductive type layer 36 are sequentially stacked on the firstconductive type layer 34 of a triangular prism shaped structure havingan approximately triangular cross-section.

[0087] The active layer 35 functions as a light emission layer of asemiconductor light emitting device, and is configured as an InGaN layeror as an InGaN sandwiched between AlGaN layers. The active layer 35 maybe configured as a single bulk active layer but may be configured as alayer having a quantum well structure such as a single quantum well(SQW) structure, a double quantum well (DQW) structure, or a multiplequantum well (MQW) structure. If the active layer 35 is configured as alayer having the multiple quantum well structure, a barrier layer may beused for separating quantum wells from each other as needed.

[0088] The second conductive type layer 36 is made from a wurtzite typecompound semiconductor such as GaN doped with magnesium. The secondconductive type layer 36 functions as a p-type cladding layer.

[0089]FIGS. 13A and 13B are a sectional view and a perspective view,respectively, showing the step of forming a p-side electrode in thefabrication method according to the second embodiment.

[0090] A p-side electrode 37 is formed on the surface of the secondconductive type layer 36, which is the outermost layer of the triangularprism shaped stacked structure composed of the first conductive typelayer 34, the active layer 35, and the second conductive type layer 36.For example, the p-side electrode 37 has a stacked metal structure ofNi/Pt/Au or Pd/Pt/Au formed by the vapor-deposition process. It is to benoted that an n-side electrode is formed on the back surface of thetriangular prism shaped stacked structure and, therefore, it is notformed in this step.

[0091]FIGS. 14A and 14B are a sectional view and a perspective view,respectively, showing the step of peeling the growth substrate and theunder growth layer from the triangular prism shaped stacked structuresby irradiating the triangular prism shaped stacked structures with laserbeams traveling from the back side of the growth substrate in thefabrication method according to the second embodiment.

[0092] To peel the growth substrate 31 and the under growth layer 32from the triangular prism shaped stacked structures, laser beams such asexcimer laser beams as ultraviolet laser beams or higher harmonic YAGlaser beams are emitted to the back side of the growth substrate 31. Thelaser beams may be emitted to the overall back surface of the growthsubstrate 31 or be selectively emitted to regions, corresponding totarget semiconductor light emitting devices, of the back surface of thegrowth substrate 31.

[0093] Since the band gap energy of the first conductive layer 34 is, asdescribed above, smaller than that of the under growth layer 32, iflaser beams having an energy value between these band gap energies isused as the laser beams emitted to the back side of the growth substrate31, the laser beams are not absorbed by the under growth layer 32 butare absorbed by the first conductive type layer 34. Accordingly, since afirst conductive type layer 34 side interface between the under growthlayer 32 and the first conductive type layer 34 absorbs the laser beams,abrasion occurs at the first conductive type layer 34 side interface,with a result that the growth substrate 31 is peeled, together with theunder growth layer 32, from the triangular prism shaped stackedstructures.

[0094] In the case where the under growth layer 32 is made from AlGan(Al content: about 15%) and the first conductive type layer 34 is madefrom GaN having band gap energy smaller than that of AlGaN, if thirdharmonic YAG laser beams (355 nm) are emitted to the back side of thegrowth substrate 31, the first conductive type layer 34 side interfacebetween the under growth layer 32 and the first conductive type layer 34absorbs the YAG laser beams, so that GaN is decomposed into gallium (Ga)and nitrogen at the first conductive type layer 34 side interface, withthe result that the growth substrate 31 and the under growth layer 32are easily peeled from the triangular prism shaped stacked structures.

[0095] The band gap energy of AlGaN (Al content: about 15%) forming theunder growth layer 32 is 3.8 eV, the band gap energy of GaN forming thefirst conductive type layer 34 is 3.2 eV, and the energy of the thirdharmonic YAG laser beams (355 nm) is 3.5 eV. Accordingly, the YAG laserbeams are not absorbed by the under growth layer 32 but absorbed by thefirst conductive type layer 34, with a result that abrasion occurs atthe first conductive layer 34 side interface.

[0096] As described above, when the triangular prism shaped stackedstructure including the first conductive layer 34 made from asemiconductor material having band gap energy smaller than that of theunder growth layer 32 is irradiated with laser beams having an energyvalue between the band gap energies of the two layers 32 and 34, thelaser beams are not absorbed by the under growth layer 32 but absorbedby the first conductive type layer 34. Accordingly, the first conductivetype layer 34 side interface between the under growth layer 32 and thefirst conductive type layer 34 absorbs the laser beams, and therebyabrasion occurs at the first conductive type layer 34 side interface,with a result that the growth substrate 31 and the under growth layer 32are easily peeled from the triangular prism shaped stacked structure.

[0097] Each of the triangular prism shaped stacked structures, which iscomposed of the first conductive layer 34, the active layer 35, and thesecond conductive layer 36 formed by selective growth, is bonded to thegrowth substrate 31 via the under growth layer 32. However, thesetriangular prism shaped stacked structures are separated from eachother. Accordingly, when peeled from the growth substrate 31 and theunder growth layer 32, the triangular prism shaped stacked structuresare simultaneously isolated from each other.

[0098] As a result, a number of triangular prism shaped stackedstructures, each containing a number of semiconductor light emittingdevices, can be efficiently peeled from the growth substrate 31 and theunder growth layer 32 and simultaneously isolated from each other.

[0099]FIGS. 15A and 15B are a sectional view and a perspective view,respectively, showing the step of forming an n-side electrode in thefabrication method according to the second embodiment.

[0100] The back surface of each triangular prism shaped stackedstructure containing a number of a semiconductor light emitting devicesis etched with acid or the like, and an n-side electrode 38 typicallyhaving a Ti/Al/Pt/Au electrode structure is formed thereon by thevapor-deposition process or the like.

[0101] After being peeled from the growth substrate 31 and the undergrowth layer 32, each triangular prism shaped stacked structure havingan approximately triangular cross-section, which is composed of thefirst conductive type layer 34, the active layer 35, and the secondconductive type layer 36, is cut in the direction perpendicular to theridge line of the stacked structure into a number of semiconductor lightemitting devices by dicing or etching.

[0102] In this case, a cleavage plane functioning as a resonance endplane of a semiconductor laser can be formed by cleavage describedbelow.

[0103] By making use of the above-described peeling and isolating methodfor a semiconductor light emitting device using laser irradiation, asshown in FIGS. 16A and 16B, it is possible to peel a desiredsemiconductor light emitting device of the triangular prism shapedstacked structure from the growth substrate 31 and the under growthlayer 32 by irradiating the device portion with laser beams from theback side of the growth substrate 31 and simultaneously form a cleavageplane functioning as a resonance end plane of a semiconductor laser onan end plane of the device.

[0104]FIG. 16A is a perspective view showing the step of peeling thedesired two devices contained in the two triangular prism shaped stackedstructures adjacent to each other from the growth substrate 31 and theunder growth layer 32, and FIG. 16B is a bottom view showing a laserbeam irradiation region irradiated with laser beams to peel the desiredtwo devices from the growth substrate 31 and the under growth layer 32.

[0105] As shown in FIG. 16B, a laser beam irradiation region 40 in whichdesired devices 41 a and 41 b are located is irradiated with laser beamstraveling from the back side of the growth substrate 31. At this time,the devices 41 a and 41 b located in the laser beam irradiation region40 are irradiated with the laser beams, and thereby peeled from thegrowth substrate 31 and the under growth layer 32 due to abrasiondescribed above. On the other hand, device portions adjacent to each ofthe devices 41 a and 41 b, which are located out of the laser beamirradiation region 40, of the triangular prism shaped stacked structureare not irradiated with the laser beams and thereby are not peeled fromthe growth substrate 31 and the under growth layer 32. Accordingly, theinterface plane between each of the devices 41 a and 41 b and the deviceadjacent thereto is cleaved in the direction perpendicular to a ridgeline 39 of the triangular prism shaped stacked structure composed of thefirst conductive type layer 34, the active layer 35, and the secondconductive type layer 36, to form a pair of cleavage planes functioningas resonance end planes of a semiconductor laser on the end planes ofeach of the devices 41 a and 41 b as shown in FIG. 16A.

[0106] In this way, by irradiating the desired devices 41 a and 41 bwith laser beams, it is possible to efficiently peel the devices 41 aand 41 b from the growth substrate 31 and the under growth layer 32 andsimultaneously form a pair of cleavage planes functioning as resonanceend planes on the end planes of each of the devices 41 a and 41 b.

[0107] The method according to the second embodiment described above hasthe following advantages.

[0108] Since the band gap energy of the first conductive type layer 34is smaller than that of the under growth layer 32, when the laser beamshaving an energy between the band gap energies of the layers 32 and 34are emitted to the back side of the growth substrate 31, the laser beamsare not absorbed by the under growth layer 32, but by the firstconductive layer 34. Accordingly, the first conductive type layer 34side interface between the under growth layer 32 and the firstconductive type layer 34 absorbs the laser beams, whereby abrasionoccurs at the first conductive type layer 34 side interface. As aresult, the growth substrate 31 can be simply peeled, together with theunder growth layer 32, from the triangular prism shaped stackedstructure, and the n-side electrode 38 can be efficiently formed on theexposed back surface of the first conductive type layer 34 of the peeledhexagonal pyramid shaped stacked structure.

[0109] Each of the triangular prism shaped stacked structures, which iscomposed of the first conductive layer 34, the active layer 35, and thesecond conductive layer 36 formed by selective growth, is bonded to thegrowth substrate 31 via the under growth layer 32. However, thesehexagonal pyramid shaped stacked structures are separated from eachother. Accordingly, when peeled from the growth substrate 31 and theunder growth layer 32, the triangular prism shaped stacked structuresare simultaneously isolated from each other.

[0110] As a result, according to the second embodiment, a number oftriangular prism shaped stacked structures, each containing a number ofsemiconductor light emitting devices, can be efficiently peeled from thegrowth substrate 31 and the under growth layer 32 and simultaneouslyisolated from each other.

[0111] Further, by selectively irradiating a desired device portion ofthe triangular prism shaped stacked structure composed of the firstconductive type layer 34, the active layer 35, and the second conductivetype layer 36, it is possible to peel the device from the growthsubstrate 31 and the under growth layer 32 and simultaneously form apair of cleavage planes functioning as resonance end planes of asemiconductor laser on the end planes of the device.

[0112] Although the present invention has been described with referenceto specific embodiments, those of skill in the art will recognize thatchanges may be made thereto without departing from the spirit and scopeof the present invention as set forth in the hereafter appended claims.

1. A method of fabricating a semiconductor device, the method comprisingthe steps of: forming an under growth layer on a substrate; forming ananti-growth film having a specific opening portion on the under growthlayer; forming a first conductive type layer by selective growth fromthe opening portion, the first conductive type layer having a band gapenergy smaller than that of the under growth layer; stacking an activelayer and a second conductive type layer on the first conductive typelayer to form a stacked structure; and peeling the stacked structurefrom the substrate and the under growth layer at an interface betweenthe under growth layer and the first conductive type layer byirradiating the stacked structure with light rays traveling through thesubstrate.
 2. A method of fabricating a semiconductor device as claimedin claim 1, wherein each of the under growth layer, the first conductivetype layer, the active layer and the second conductive type layer is awurtzite type compound semiconductor layer.
 3. A method of fabricating asemiconductor device as claimed in claim 2, wherein the wurtzite typecompound semiconductor layer is a nitride based compound semiconductorlayer.
 4. A method of fabricating a semiconductor device as claimed inclaim 1, wherein the under growth layer is made from AlGaN and the firstconductive type layer is made from GaN.
 5. A method of fabricating asemiconductor device as claimed in claim 1, wherein at least the activelayer extends within a plane parallel to a tilt crystal plane tiltedfrom a principal plane of the substrate.
 6. A method of fabricating asemiconductor device as claimed in claim 1, wherein the substrate haslight permeability.
 7. A method of fabricating a semiconductor device asclaimed in claim 1, wherein the stacked structure is irradiated with thelight rays traveling from a back side of the substrate.
 8. A method offabricating a semiconductor device as claimed in claim 1, wherein thepeeling of the stacked structure from the substrate and the under growthlayer is made by abrasion caused by light irradiation.
 9. A method offabricating a semiconductor device as claimed in claim 1, wherein thelight rays have an energy value between a band gap energy of the undergrowth layer and a band gap energy of the first conductive type layer.10. A method of fabricating a semiconductor device as claimed in claim1, wherein the light rays are laser beams.
 11. A method of fabricating asemiconductor device as claimed in claim 10, wherein the laser beamshave a wavelength ranging from 340 nm to 360 nm.
 12. A method offabricating a semiconductor device as claimed in claim 1, wherein oneelectrode is formed on a peeled back surface of the first conductivelayer of the stacked structure to form a semiconductor device.
 13. Amethod of fabricating a semiconductor device as claimed in claim 1,wherein a cleavage plane of the stacked structure for forming asemiconductor device is formed by peeling the stacked structure from thesubstrate and the under growth layer.
 14. A method of fabricating asemiconductor device as claimed in claim 1, wherein the cleavage planebecomes a resonance end plane of the semiconductor device.
 15. Asemiconductor device, comprising: an under growth layer formed on asubstrate; an anti-growth film, having a specific opening portion,formed on the under growth layer; a first conductive type layer formedby selective growth from the opening portion, the first conductive typelayer having a band gap energy smaller than that of the under growthlayer; and an active layer and a second conductive type layer stacked onthe first conductive type layer to form a stacked structure; wherein thestacked structure is peeled from the substrate and the under growthlayer at an interface between the under growth layer and the firstconductive type layer by irradiating the stacked structure with lightrays traveling through the substrate.
 16. A semiconductor device asclaimed in claim 15, wherein each of the under growth layer, the firstconductive type layer, the active layer and the second conductive typelayer is a wurtzite type compound semiconductor layer.
 17. Asemiconductor device as claimed in claim 16, wherein the wurtzite typecompound semiconductor layer is a nitride based compound semiconductorlayer.
 18. A semiconductor device as claimed in claim 15, wherein theunder growth layer is made from AlGaN and the first conductive typelayer is made from GaN.
 19. A semiconductor device as claimed in claim15, wherein at least the active layer extends within a plane parallel toa tilt crystal plane tilted from a principal plane of the substrate. 20.A semiconductor device as claimed in claim 15, wherein the substrate haslight permeability.
 21. A semiconductor device as claimed in claim 15,wherein the stacked structure is irradiated with the light raystraveling from a back side of the substrate.
 22. A semiconductor deviceas claimed in claim 15, wherein the peeling of the stacked structurefrom the substrate and the under growth layer is made by abrasion causedby light irradiation.
 23. A semiconductor device as claimed in claim 15,wherein the light rays have an energy value between a band gap energy ofthe under growth layer and a band gap energy of the first conductivetype layer.
 24. A semiconductor device as claimed in claim 15, whereinthe light rays are laser beams.
 25. A semiconductor device as claimed inclaim 24, wherein the laser beams have a wavelength ranging from 340 nmto 360 nm.
 26. A semiconductor device as claimed in claim 15, whereinone electrode is formed on a peeled back surface of the first conductivelayer of the stacked structure to form a semiconductor device.
 27. Asemiconductor device as claimed in claim 15, wherein a cleavage plane ofthe stacked structure for forming a semiconductor device is formed bypeeling the stacked structure from the substrate and the under growthlayer.
 28. A semiconductor device as claimed in claim 15, wherein thecleavage plane becomes a resonance end plane of the semiconductordevice.